This procedure covers removal and replacement of the front differential pinion seal on a 2011-2014 Ford F-150 3.5L EcoBoost 4WD to correct fluid leaks from the pinion shaft.

Warnings

Tools required

Parts

• Front differential pinion seal × 1 — Use OEM specification
• 75W-90 GL-5 gear oil × 1 — Use OEM specification
• RTV silicone gasket maker (if needed) × 1 — Use OEM specification

Fluids

• 75W-90 GL-5 Gear Oil — 1.5 qt

Preparation

1. Park vehicle on level ground and apply parking brake
2. Place wheel chocks behind rear wheels
3. Raise front of vehicle and support securely on jack stands at frame contact points
4. Remove front wheels to improve access
5. Allow differential to cool completely if vehicle was recently driven
6. Clean exterior of differential housing around pinion area to prevent contamination

Procedure

1. 1

   Mark and measure pinion preload
   Using a paint marker, mark the relationship between the pinion shaft, pinion nut, and pinion flange for reassembly reference. Using an inch-pound torque wrench, measure and record the rotational torque required to turn the pinion (pinion bearing preload). Rotate the pinion several complete revolutions and note the continuous rotating torque, not the breakaway torque. This value is typically 5-20 in-lb and MUST be matched during reassembly.
2. 2

   Remove driveshaft
   Mark the driveshaft and pinion flange relationship for proper reinstallation phasing. Remove the four U-joint strap bolts connecting the front driveshaft to the differential pinion flange. Support the driveshaft and carefully lower it away from the pinion flange. Secure the driveshaft out of the way using wire or a bungee cord to prevent damage to the CV joint boot.
   ⚠Do not allow the driveshaft to hang unsupported as this can damage the center support bearing or CV joint.
   Torque spec

   Driveshaft U-Joint Straps20 Nm (15 lb-ft)
3. 3

   Remove pinion nut
   Using a pinion flange holding tool or large channel locks to prevent rotation, remove the pinion nut with a breaker bar and appropriate socket. The nut is torqued to very high specification and will require significant force. Once loose, remove the nut completely and set aside. Note: This nut may be reused if not damaged, but the pinion bearing preload must be verified during reassembly.
   ⚠The pinion flange is under tension from the pinion bearing preload. Control the flange as you remove the nut.
4. 4

   Remove pinion flange
   With the nut removed, pull the pinion flange straight off the pinion shaft. Some flanges are slip-fit and will pull off by hand; others may require gentle persuasion with a puller or careful prying. Do not damage the pinion shaft threads. If the flange is tight, use a two-jaw puller on the flange face. Once removed, inspect the flange seal surface for grooves or damage that could cause the new seal to leak.
5. 5

   Drain differential fluid
   Place a drain pan under the differential. With the pinion flange removed, fluid will begin to drain from the pinion seal area. Allow sufficient time for fluid to drain. You may need to remove the differential cover fill plug or cover to allow complete drainage and air entry. Expect approximately 1-1.5 quarts to drain.
6. 6

   Remove old pinion seal
   Using a seal puller or carefully with a large flat-blade screwdriver, pry the old pinion seal out of the differential housing. Work around the seal circumference to extract it evenly. Be careful not to damage the seal bore in the housing. Clean the seal bore thoroughly with a clean rag, removing all old seal material, dirt, and debris. Inspect the bore for damage or burrs.
   ⚠Do not score or gouge the seal bore surface. Any damage to this surface will cause the new seal to leak.
7. 7

   Install new pinion seal
   Lightly coat the outer diameter of the new pinion seal with gear oil. Verify the seal is oriented correctly with the spring side toward the differential fluid (inside). Using a pinion seal installation tool or an appropriately-sized deep socket that contacts only the outer edge of the seal, drive the seal squarely into the bore until it seats fully. The seal should be flush with or slightly below the housing face. Apply a thin coat of gear oil to the seal lip.
8. 8

   Reinstall pinion flange
   Inspect the pinion flange seal surface for wear grooves. If grooves are present, the flange must be replaced. Clean the pinion shaft splines and the flange splines. Align the flange with your earlier paint marks and slide it onto the pinion shaft, ensuring proper engagement of the splines. The flange should slide on with moderate hand pressure.
9. 9

   Install pinion nut and set preload
   Install the pinion nut and tighten in stages while frequently checking pinion bearing preload. Hold the flange and tighten the nut gradually. After each incremental tightening, rotate the pinion several revolutions to seat the bearings, then measure rotating torque with the inch-pound torque wrench. Continue tightening until the rotating torque matches your original measurement from Step 1 (typically 5-20 in-lb). The nut should align approximately with your paint marks. Do not exceed the original preload value.
   ⚠️Over-tightening the pinion nut will collapse the bearing spacer and destroy the pinion bearings. If you exceed the target preload, the differential must be disassembled and the crush sleeve replaced. Never back off the nut to reduce preload.
10. 10

    Reinstall driveshaft
    Position the driveshaft to the pinion flange, aligning the marks made during disassembly to maintain proper driveshaft phasing. Install the four U-joint strap bolts and tighten evenly in a cross pattern to specification. Verify the driveshaft rotates freely without binding.
    Torque spec

    Driveshaft U-Joint Straps20 Nm (15 lb-ft)
11. 11

    Refill differential
    Locate the differential fill plug on the front or side of the housing. Remove the fill plug and add 75W-90 GL-5 gear oil until it reaches the bottom of the fill hole (fluid should just begin to seep out). The front differential capacity is approximately 1.5 quarts. Reinstall and tighten the fill plug. If the differential cover was removed, install a new gasket or apply RTV silicone per manufacturer instructions and reinstall cover bolts to specification.
    Torque spec

    Differential Cover Bolts35 Nm (26 lb-ft)
12. 12

    Reinstall wheels and lower vehicle
    Reinstall the front wheels, threading lug nuts by hand initially. Lower the vehicle until the tires just contact the ground. Torque the lug nuts to specification in a star pattern. Fully lower the vehicle and remove jack stands.
    Torque spec

    Wheel Lug Nuts140 Nm (103 lb-ft)

Reassembly

1. Ensure all torque specifications have been met, particularly the driveshaft U-joint straps and wheel lug nuts
2. Verify pinion bearing preload matches the original measured value
3. Double-check that the differential is filled to the proper level

Verification

• Start the engine and shift through all drive ranges including 4WD to circulate fluid through the differential
• Test drive the vehicle for 5-10 miles, making several turns in both directions
• Re-check the differential fluid level after test drive and top off if necessary
• Inspect the pinion seal area for any signs of leakage immediately after test drive and again after 24 hours
• Listen for any unusual noises from the front differential during operation which could indicate incorrect pinion bearing preload

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